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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 260738

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sun Sep 26 2021

Tropical Weather Discussion for the eastern Pacific Ocean from
03.4S to 30N, east of 120W including the Gulf of California, and
from the Equator to 30N, between 120W and 140W. The following
information is based on satellite imagery, weather observations,
radar, and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0730 UTC.


A tropical wave is along 96W, from 02N to 15N, moving west at
around 10 kt. Precipitable water animations and wave diagnostics
show a clear wave signal propagating westward off of Central 
America the past couple of days. Associated convection is 
described below.


The monsoon trough extends from northern Colombia from 1009 mb
low pressure near 10.5N74W to across northern Costa Rica and the
Papagayo region at 10N86W to 10N110W to 12N120W to 09N134W. The 
ITCZ extends from 09N134W to 08N140W. Scattered moderate and
isolated strong convection is noted from 02N to 09N between 77W
and 81W, from 12N to 14N between 88W and 92W, from 05N to 13N
between 94W and 105W, from 13N to 17N between 97W and 100W, and
from 07N to 16N between 117W and 133W.

Similar convection is noted from 17N to 24N between 103W and


Fresh to near gale force N-NE winds are noted in the Gulf of 
Tehuantepec along with seas of 5 to 8 ft. Moderate NW-N winds are
noted west of Baja California and in the central and southern 
Gulf of California. Light to gentle winds are noted elsewhere. 
Seas are 4 to 7 ft across the remainder of the open waters, and 2
to 4 ft in the Gulf of California, except 3 ft or less in the 
northern Gulf.

For the forecast, fresh to strong northerly gap winds will 
continue across the Gulf of Tehuantepec through tonight. Mainly 
moderate NW-N winds will prevail west of Baja California, pulsing
to fresh during the afternoon through evening hours. S-SW winds 
will pulse to moderate to fresh in the northern Gulf of 
California. Otherwise, gentle to moderate winds will prevail. 
Large NW swell will impact the waters west of Baja California by 
late Tue. 


Fresh to locally strong offshore winds prevail across the 
Papagayo region, with light to gentle winds elsewhere north of 
the monsoon trough. Gentle to moderate S-SW winds are south of 
the monsoon trough. Seas are in the 4 to 6 ft range from offshore
of Colombia northward, and 5 to 7 ft in SW swell offshore of 

For the forecast, moderate to fresh offshore winds will pulse 
across the Papagayo region, occasionally to strong. Otherwise, 
light to gentle winds will prevail north of the monsoon trough, 
with mainly moderate winds south of the monsoon trough. Cross 
equatorial SW swell will propagate through the regional waters 
through early Tue.


A surface trough extends from 23N130W to 1014 mb low pressure
near 20N132W to 16N131W. Associated convection has dissipated.
Moderate to locally fresh NE-E winds are northwest of the 
trough. Broad and weak ridging and gentle to moderate trades 
dominate the remainder of the open waters north of the 
convergence zone. Gentle to moderate southerly winds prevail 
south of the convergence zone. Seas are in the 5 to 7 ft range 
north of 11N, and 6 to 7 ft south of 11N, except locally to 8 ft 
between 93W and 115W.

For the forecast, winds associated with the trough along 130W 
will gradually diminish through late Sun as it shifts westward 
and weakens. A cold front is expected to move into the NW waters 
Mon night into early Tue and quickly weaken as it moves southward
and gradually dissipates along 21N by the end of the week. 
Associated long period NW swell is expected to build seas to 8 to
11 ft to the west of 120W, spreading southward through the 
middle of this coming week.